ZOO 115 Invertebrate Zoology Phylum Platyhelminthes

Classes Turbellaria Mongenea Trematoda Cestoda Free-living flatworms Mongenetic flukes - parasitic Trematoda Flukes- parasitic Cestoda Tapeworms- parasitic

Phylum Platyhelminthes © David Luquet /gecko.gc.maricopa.edu/~lsola/bio182/labreview/ www.pbs.org/kcet/shapeoflife/imganim/ Ed T. Schmidtmann, USDA/ARS. www.islandream.com/wakatobi/flatworm02.jpg

Phylum Platyhelminthes About 20,000 sp. Substrate crawlers in both marine and freshwater Mostly small and soft-bodied Lack a circulatory system Diffusion limited Controversy about phylogeny

Platyhelminthes Class Turbellaria www.seafriends.org.nz/enviro/habitat/f017217t.jpg Virtually all are aquatic with most being marine Most are bottom dwellers but there are some pelagic forms

Body Outer-layer is a ciliated epidermis Skeleton – weblike sheet of actin filaments Secrete Rhabdites Thought to be important in locomotion, cocoon development and predator repellant

Body Gland cells Mesenchyme – Hydraulic action on larger organisms zoology.unh.edu/faculty/litvaitis/Flatworms/muscles.jpg Gland cells Gland cells zoology.unh.edu/faculty/litvaitis/Flatworms/muscles.jpg Mesenchyme – Hydraulic action on larger organisms Parenchyma – connective tissue compartment between body wall, musculature and gut. Neoblasts - wound repair and regeneration Chromatophores may be present and under control by brain.

Nervous system Bilaterial or Ring like brain Longitudinal nerves Nerve net

Nervous system - sensory Chemoreceptors over entire body Cilia mechanoreceptors Ocelli Some have statocysts in the head region

Musculature Also have diagonal muscles – not shown Longitudinal muscles zoology.unh.edu/faculty/litvaitis/Flatworms/muscles.jpg Dorsoventral muscles Circular muscles

How do they move? Ciliary creeping Muscular creeping Swimming Peristalsis Twisting, turning, extension and retraction Somersaulting

Complete Bilateral gut www.emc.maricopa.edu/faculty/farabee/BIOBK/flatworm.gif www.emc.maricopa.edu/faculty/farabee/BIOBK/flatworm.gif zoology.unh.edu/faculty/litvaitis/Flatworms/muscles.jpg Gut

Feeding and digestion Food swallowed by pharynx or www.emc.maricopa.edu/faculty/farabee/BIOBK/flatworm.gif Sense prey using chemreceptors and mechanoreceptors Capture prey Wrapping themselves around prey Entangling it in slime Pinning prey with adhesive glands Some have toxic mucus Some use penis Most are carnivores and scavengers Some Aoela have zooxanthellae Proteolytic enzymes are injected into prey and pharynx is used to pump liquified contents. Gut types Acoela – syncytial mass enclosed by membrane Simple unbranched sac Multiple lateral branches Gland cells in gut supply additional enzymes. Digestive cells phagocytize remainder

Excretion www.lifesci.utexas.edu/faculty/sjasper/images/protonephridia.jpg

Reproduction Regeneration Clonal Reproduction – longitudinal fission

Reproduction Sexual Reproduction Most hermaphrodites Most copulation and internal fertilization Male 1 or more pairs of testis Ducts, storage area Penis – may have stylet Female I or more pairs of ovaries Copulatory bursa (vagina), seminal receptacle, uterus

Reproduction Development Some freshwater species produce summer and winter eggs Usually egg->blastula->gastrula->juvenile->adult Marine polyclads produce planktonic larvae Generation time: 16-75 days Life span: 65-140 days

Platyhelminthes – Dueling Penises Wounds Penis